3 months no delivery, no refund

I have been battling for 3 months to either get the items delivered or a refund. It took the courier 3 weeks to deliver 7 boxes of 6 x 1lt long life milk. When they delivered it was someone else's order and partial delivery. They collected it the next day and since then it has been escalated on a weekly basis, sometimes twice a week. No delivery no refund. Each time I have to explain the issue to a new operator and they re-escalate. Seriously pathetic and worst service ever!!! Each order is a issue, it never used to be like this.